Electrical resistance.



UNITED STATES PATENT orrion.

ELIHU THOMSON, or SWAMPSCOTT, MASSACHUSETTS, ASSIGNOR TO GENER ELECTRICCOMPANY, A CORPORATION on NEW YORK.

ELECTRICAL RESISTANCE.

Specification of Letters Patent.

Patented June 3, 1913..

' To all whom it may concern:

Be it known that I, ELIHU THOMSON, a citizen of the United States,residing at Swampscott, county of Essex, State of Massachusetts, haveinvented certain new and useful Improvements in Electrical Resistances,of which the following is a specification.

This invention relates to electrical resistances and has for its objectthe provision of a unit which will have a high resistance, is simple andinexpensive to construct and at the same time, very etiicient anddurable.

My invention relates more specifically to resistance materials whichhave a high resistance and low heat conductivity. Such materials, forinstance, as boron, have a high resistance and also a high negativetemperature resistance co-efficient and low heat conductivity. Becauseof this combination of physical properties, such a material will allowbut a very small leakage current to pass until the impressed voltageexceeds a certain break-down value and when this voltage is exceeded theresistance very suddenly falls to a lowv value. In the meet thismaterial, especially in large sections, it is found that the currentwill concentrate in a particular part of the section, instead of flowinguniformly over it.

-The object of my invention, therefore, is to overcome this objection byarranging a heat conducting material 50 that it will conduct the heatuniformly throughout the sections.

In carrying out my invention I employ layers of resistance material andplace between the layers a good heat conducting material. The layers arearranged alternately so as to form a complete unit and pressed togetherin some manner, as for instance, by a springpressure.

In the accompanying drawings in which I have shown my invention embodiedin concrete form for purposes of illustration, Figure 1 represents acomplete unit, partly broken away; Fig. 2 shows two of the elementscomposing the unit in perspective;

F ig. 3 shows a modified form of element; and Fig. t shows still anotherform.

Referring to the drawings, 10 represents a layer or plate of resistancematerial such as boron or the like. This material has a h co-efiicientand low heat conductivity, A

resistance, but a negative temperature plurality of these disks 10 arearranged alternately, as shown in Fig. 1, with a plurality of similarlyshaped plates of metal having a high heat conductivity. I have foundthat where boron is used as the resistance element copper plates 11serve the purpose of heat radiators or conductors, as its heatconductivity is high and it does not combine with the boron. Thesealternate plates or disks 10 and 11 are mounted between brackets 12 and13 and pressed together by means of a spring 14. One terminal connectionis made at having a plate 16 which is pressed against the uppermostcopper plate and the other terminal connection is made at 17 with thelowermost copper plate, as shown. In this manner the heat which isdeveloped in the resistance plates 10 is distributed throughout theplate and a more uniform resistance,

combined with a uniform heat, is obtained.

Instead of applying the alternate disks as shown in Figs. 1 and 52,substantially the same result may be obtained by coating one side of themetallic plate with boron, as shown in Fig. 3. In Fig. 4:, I have shownanother method of accomplishing this result, wherebythe heat isdissipated rapidly. In this case the resistance plate 18 is clampedbetween two conducting plates 19 and separated from thenext element byan air gap so as to surface. 'The underlying principle is the same,however, as in the form shown in Figs. 1 and 2, namely, the furnishingof heat'conducting means for causing the re' sistance material to be ofuniform temperature.

- While I .have described my invention as embodied in concrete form andemploying specific materials for purposes of illustration, it should beunderstood that I do not limit my invention thereto, since variousmodifications thereof will suggest themselves to those skilled in theart without departing from the spirit of my invention, the scope ofwhich is set forth in the annexed claims.

furnish a large radiating What I claim as new and desire to secure byLetters Patent of the United States, is,-

1. In a reslstance unit, the combination of a material having a high"cold resistance and a high negative temperature resistance coeflicientsimilar to boron, and a body of material having better heat conductivitythan 'loorori in thermal and electric conductive relation thereto.

2. The combination of adliskof looron material, and a metallic elisk ofgood heat 5 conductivity in contact therewith. 3. The combination of aplurality of 1 plates of material of the nature of boron in itselectrical break-down characteristics and a plurality of heat radiatorsin thermal-and electrical contact with said, plates. 10 I in Witnesswhereof, I have hereunto set my hand this first day of July, 1909.

ELIHU THUMSUN. Witnesses:

JOHN A. MoMANUs, Jr., QHARLES A. BARNARD.

